THINGS are still sizzling between fifth-season “Top Chef” contestant Leah Cohen and winner Hosea Rosenberg. The duo, who were caught kissing on camera during the show (although they were each dating someone else at the time), kept the flame burning Saturday night when they saw “Fuerza Bruta” together. “It was just the two of them,” said our spy, “and they were kissing all night.” Rosenberg was visiting Manhattan-based Cohen from Boulder, Colo., where he’s the chef at Jax Fish House. Rosenberg’s rep didn’t return calls and Cohen couldn’t be reached.